The following investigations are proposed: 1. To quantitate the levels of estrogen and progesterone receptors in normal endometrium, hyperplastic endometrium, endometrial carcinoma, and breast carcinoma. The data will be used to evaluate the correlation of critical levels of estrogen and/or progesterone receptors in endometrial and breast tumors with the patients' response to endocrine therapy. 2. The association of estrogens with endometrial cancer will be examined by measuring estrone and estradiol levels in plasma, whole endometrial tissue and endometrial nuclei, as well as estrone-estradiol interconversions in the endometrium of patients with hyperplasia and carcinoma. 3. The mechanisms involved in the objective remission of endometrial tumors by progestational agents will be investigated by studying the following parameters in tumor tissue before and after progestin therapy: levels of estrogen receptors; levels of estrone and estradiol; estrone-estradiol interconversion; uptake and intracellular distribution of estrone and estradiol.